CODEWITHSUNDEEP
redisadditionsortedset
category
category

Reputation: 2155

ZADD member with highest score

Is it possible (or is there another idiomatic way) to ZADD a member with a score of the highest existing score plus one?

For example:

> FLUSHDB
> ZADD key 1 one
> ZADD key * mem
> ZSCORE key mem
1) "2"

Upvotes: 0

Views: 416

Answers (1)

for_stack
for_stack

Reputation: 22906

You can use zrevrange to get the largest score, and then call zadd to set the score to be largest + 1. There's no built-in way to do that. However, you can write a Lua script to do the job:

local key = KEYS[1]
local field = ARGV[1]
local score = ARGV[2]

if score then
    -- client specifies a score, use it
    redis.call('zadd', key, score, field)
else
    -- get the largest score in the sorted set
    local largest = redis.call('zrevrange', key, 0, 0, 'withscores')
    score = largest[2]
    if score then
        -- update the score
        score = score + 1
    else
        -- the sorted set is empty, set a default score
        score = 0
    end
    redis.call('zadd', key, score, field)
end

Try it: ./src/redis-cli --eval t.lua key , field

Upvotes: 2

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